曝气对人工湿地氮去除效果的影响   总被引：5，自引：0，他引：5  

方焰星  何池全  梁霞  金海  詹跃武  张亚克  张绚璇 《湿地科学》2011,9(3):270-276

选择不同的植物组合,分别在6组复合垂直流人工湿地的下行池、上行池种植金边石菖蒲(Acorus gramineus)、宽叶泽苔(Caldesia renif ormis);慈姑(Sagittaria sagittif olia)、水葱(Scirpus validus);灯芯草(Juncus effuses)、梭鱼草(Po...  相似文献   

开发区土地集约利用强度潜力分析——以桐梓县娄山关经济开发区为例     

张杭杭  周国富 《西部资源》2011,(5):44-45

本文以桐梓县娄山关经济开发区为例,在对开发区进行实地调查的基础上,计算该开发区的工业用地容积率、建筑系数和固定资产投入、产出强度的现状值,然后通过综合考虑确定其目标值,采用目标直逼法,测算出开发区各类强度潜力值,最后对其结果进行分析,以此提出开发区未来发展的对策与建议。  相似文献   

1998-2012年中国耕地复种指数时空差异及动因   总被引：7，自引：0，他引：7  

谢花林  刘桂英 《地理学报》2015,(4)

从国家、区域和省级三个层面上分析了1998-2012年间中国耕地复种指数的变化趋势,并基于Theil指数探讨了中国耕地复种指数的时空差异,利用计量经济学模型从人文视角探讨了耕地复种指数变化的影响因素。结果表明:1在全国尺度上,中国耕地复种指数总体上呈逐年增长的趋势。2在区域尺度上,复种指数最高的为中部地区,最低的为东北地区;而复种指数增长最快的是东北地区,最慢的是中部地区,东部地区呈下降趋势。3中国31个省份复种指数各不相同,且差距大,复种指数增长最快的是新疆、宁夏和云南。4由Theil指数值的大小可知,中国耕地复种指数的差异呈缩小态势,其主要原因为四大区域间的差异。5人口非农化比重对耕地复种指数产生了显著负向作用,产业非农化比重、农业政策、人均经营耕地和农村家庭人均经营纯收入对耕地复种指数产生了显著正向作用。最后,本文认为转移农村剩余劳动力,提高农民的经营性收入水平,促进土地流转,形成土地规模化经营,以及进一步加大对欠发达地区及粮食主产区农业发展的惠农扶持力度,充分发挥国家惠农政策的诱致作用,有利于全面提高中国耕地复种水平。  相似文献   

Palaeoflood activity and climate change over the last 1400 years recorded by lake sediments in the north‐west European Alps     

B. Wilhelm  F. Arnaud  P. Sabatier  O. Magand  E. Chapron  T. Courp  K. Tachikawa  B. Fanget  E. Malet  C. Pignol  E. Bard  J. J. Delannoy 《第四纪科学杂志》2013,28(2):189-199

A high‐resolution sedimentological and geochemical study of a high‐altitude proglacial lake (Lake Blanc, Aiguilles Rouges, 2352 m a.s.l.) revealed 195 turbidites, 190 of which are related to flood events over the last 1400 years. We used the coarsest sediment fraction of each turbidite as a proxy for the intensity of each flood event. Because most flood events at this locality are triggered by localized summer convective precipitation events, the reconstructed sedimentary record reveals changes in the frequency and intensity of such events over the last millennium. Comparisons with other temperature, palaeohydrological and glacier reconstructions in the region suggest that the most intense events occurred during the warmest periods, i.e. during the Medieval Climate Anomaly (AD 800–1300) and the current period of global warming. On a multi‐decadal time scale, almost all the flood frequency peaks seem to correspond to warmer periods, whereas multi‐centennial variations in flood frequency appear to follow the regional precipitation pattern. Consequently, this new Alpine flood record provides further evidence of a link between climate warming and an increase in the frequency and intensity of flooding on a multi‐decadal time scale, whereas the centennial variability in flood frequencies is related to regional precipitation patterns. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

MODIS数据北京城区热岛监测分析   总被引：1，自引：0，他引：1  

李新芝  王萍  陈庆运 《测绘科学》2010,35(4):100-102

随着城市化进程的深入,热岛效应问题越来越严重,从而影响城市及周边地区的生态环境与气候,因此备受人们的重视。本文从2000年—2007年724幅1km分辨率的MODIS地表温度产品中选取64幅质量较好,可以代表春、夏、秋、冬四个季节的昼夜影像,制作地表温度图和选取感兴趣区域分析北京城区热岛效应。结果表明,北京市城区温度明显高于周围地区,夏季夜间最高达到3.7℃,秋季白天相对热岛强度较大,夏季、冬季夜间热岛强度要大于白天,尤其冬季较为明显。  相似文献   

Investigation into the daily precipitation variability in the Yangtze River Delta,China     

Yan‐Fang Sang  Zhonggen Wang  Zongli Li  Changming Liu  Xiaojie Liu 《水文研究》2013,27(2):175-185

In this article, by using the daily precipitation data measured at 58 meteorological stations, spatial and temporal variability of daily precipitation including zero rainfall values (called “precipitation”) and without zero rainfall values (called “rain”) and four precipitation extrema (P₀, P₂₀, P₅₀, and P₁₀₀ representing the daily precipitation with the magnitude smaller than 0.1 mm, bigger than 20 mm, 50 mm, and 100 mm per day, respectively) in the Yangtze River Delta (YRD) during 1958–2007 were analyzed, and the effects of urbanization were further investigated. Results indicate that (i) differing from the downward trends in 1958–1985, daily precipitation and rain in 1986–2007 show slowly downward trends in the mid YRD but show upward trends in the northern and southern YRD. (ii) Spatial and temporal variability of the rain is more complex than daily precipitation. Both of them become smaller but show more obvious fluctuations in 1986–2007. (iii) Urbanizations cause not only the urban rainfall island problem but also more obvious fluctuations of rain intensity in the mid YRD, reflecting more uncertainty of daily precipitation variability. (iv) Urbanizations have little effects on the variability of P₀ and P₁₀₀ but cause notable increases of P₂₀ and P₅₀. (v) The spatial variability of daily precipitation and precipitation extrema in 1958–1985 clearly shows a breakpoint at 30°20′N latitude, but the breakpoint disappears afterward because of the effects of urbanization. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

A generalized conditional intensity measure approach and holistic ground‐motion selection     

Brendon A. Bradley 《地震工程与结构动力学》2010,39(12):1321-1342

A generalized conditional intensity measure (GCIM) approach is proposed for use in the holistic selection of ground motions for any form of seismic response analysis. The essence of the method is the construction of the multivariate distribution of any set of ground‐motion intensity measures conditioned on the occurrence of a specific ground‐motion intensity measure (commonly obtained from probabilistic seismic hazard analysis). The approach therefore allows any number of ground‐motion intensity measures identified as important in a particular seismic response problem to be considered. A holistic method of ground‐motion selection is also proposed based on the statistical comparison, for each intensity measure, of the empirical distribution of the ground‐motion suite with the ‘target’ GCIM distribution. A simple procedure to estimate the magnitude of potential bias in the results of seismic response analyses when the ground‐motion suite does not conform to the GCIM distribution is also demonstrated. The combination of these three features of the approach make it entirely holistic in that: any level of complexity in ground‐motion selection for any seismic response analysis can be exercised; users explicitly understand the simplifications made in the selected suite of ground motions; and an approximate estimate of any bias associated with such simplifications is obtained. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

结合强度信息的LIDAR数据滤波方法     

袁枫  张继贤  张力  高井祥 《测绘科学》2010,35(5):39-40,34

机载激光扫描系统可以直接生成扫描区域的数字表面模型,但是为了提取数字地面模型还须对LIDAR数据进行滤波处理。本文分析了用坡度法对机载LIDAR数据进行滤波的不足,并结合LIDAR数据中的强度信息,提出了一种结合强度信息的LIDAR数据滤波方法。与坡度法相比,该方法提高了滤波的精度和效率。试验结果表明该方法计算速度快,并能够有效地滤除LIDAR数据中的地物。  相似文献   

Re‐establishment of soil water repellency after destruction by intense burning in a Mediterranean heathland (SW Spain)     

Antonio Jordán  Félix A. González  Lorena M. Zavala 《水文研究》2010,24(6):736-748

Soil water repellency has been conventionally considered as a fire‐induced effect, but an increasing number of studies have suggested that natural background repellency occurs in many soil types, and many of them have suggested that water repellency can be re‐established over time after being destroyed. An experimental fire was conducted to study changes of the soil surface during the first 18 months following intense burning. The main objectives of this paper are as follows: (1) to investigate in situ water repellency changes at three soil depths (0, 2 and 4 cm) immediately after burning; (2) to evaluate the medium‐term evolution of water repellency under field conditions; and (3) to outline the main hydrological consequences of these changes. Also, different water repellency tests (water drop penetration time, ethanol percentage test (EPT) and contact angle (CA) between water drops and the soil surface) were carried out for comparison purposes. Field experiments showed that soil water repellency was partly destroyed after intense burning. Changes were relatively strong at the soil surface, but diminished progressively with depth. Levels of water repellency were practically re‐established 18 months after burning. This suggests that water repellency in the studied area is not necessarily a consequence of fire, but can instead be a natural attribute. Finally, although limited in time, destruction of soil water repellency has important consequences for runoff flow generation and soil loss rates, and, indirectly, for water quality. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Limpets as prey: Lipophrys pholis choice for size     

Ana C. Silva  Ana C. Amador  Sónia Brazão  Claúdia Faria  Diana Boaventura 《Marine Ecology》2010,31(4):525-532

Patellid limpets are key species on rocky shores, structuring intertidal assemblages through their grazing. Their role as prey for fish is, however, often overlooked in studies of intertidal ecosystem functioning. The shanny Lipophrys pholis is a common predator of limpets on rocky shores in Northern Europe and, in this study, we examined the characteristics of its predation on limpets based on prey size. The limpet size range that adult L. pholis (10–12.5 cm) can eat was examined in the laboratory using Patella depressa in 0.2 cm classes, varying between 0.5 cm and 3.0 cm in maximum shell length. There was a limpet size refuge above 1.8 cm, while all smaller sizes were readily consumed by the shanny. The predator attacking behaviour was also examined and found to vary with prey size. Limpets up to 0.8 cm were crushed by the jaw‐constricting force and eaten whole, whereas larger prey were prised from the substratum and the body subsequently separated from the shell. To examine whether there was a L. pholis preference for P. depressa size, a two‐stage laboratory experiment was done using two size classes defined as small (0.7–0.8 cm maximum shell length) and large (1.5–1.6 cm maximum shell length). In the first stage, the predator was given each limpet size class separately. In the second stage, the fish was given a choice between the two classes. Lipophrys pholis was shown to have a preference for the large size class (1.5–1.6 cm). The average number of limpets consumed by the shanny was examined for the duration of one high‐tide typical of the central region of Portugal (≈ 4 h). On average, approximately five limpets (up to an eight limpet maximum) were consumed. The present study shows that L. pholis has a feeding preference based on limpet size, which suggests that the limpet population structure and intra‐ and inter‐specific interactions may be influenced by the shanny predation.  相似文献